Method and apparatus for ocular perfusion

ABSTRACT

Ocular perfusion during intraocular surgery of the anterior or posterior ocular cavity is optimized through the method of using a gas pump having a discernible and controllable output pressure to pressurize a reservoir of liquid infusate, which is supplied under pressure to a surgical infusion instrument for perfusion of the selected ocular chamber (Gas Forced Liquid Infusion, GFLI). The infusate selection and the infusate pressure can be controlled with a high degree of accuracy and both can be rapidly varied by audible command. Preferentially a human sensible indication of pressure is constantly available at the gas pump.

This is a continuation-in-part application of Ser. No. 099,533 filedSept. 22, 1987 entitled "PARALLEL INFUSION APPARATUS AND METHOD" U.S.Pat. No. 4,813,927, 3/21/89 and a continuation of App. Ser. No. 197,567filed May 23, 1988 entitled "METHOD AND APPARATUS FOR OCULAR PERFUSION"U.S. Pat. No. 4,900,30l, 2/13/90.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods used insurgery conducted on the eye. More particularly, the present inventionrelates to apparatus used in continuous infusion processes associatedwith such surgery. In even greater particularity, the present inventionrelates to apparatus for accurately and rapidly controlling the infusionpressure to the eye and rapidly converting between liquid and gasinfusion during such surgery.

BACKGROUND OF THE INVENTION

Intraoperative control of intraocular infusion pressure is an importantparameter in eye surgery. Liquid pressure regulation has beenaccomplished in most part using gravity-fed systems involving therelative height of the infusion bottle above the eye. A discussion ofthe development of gas infusion may be found in "Vitreous Microsurgery"by Steven Charles, M.D. in Williams & Wilkins, 1981, volume 4. As notedtherein, there are known power injectors or pumps which are capable ofmaintaining an accurate intraocular pressure during air infusion, ascompared to manual syringe injection. Such devices have also beendeveloped wherein a microcompressor is used to produce an inflow of gasdependent upon intraocular pressure.

As these advances are made in gas infusion apparatus, a need exists forcontrolled intraocular infusion method and apparatus which wouldfacilitate the interchangeability of gas infusion and liquid infusionduring surgery on the posterior segment of the eye (vitrectomy).Additionally, during surgery on the anterior chamber of the eye(cataract extraction) the need exists for more accurate, surgeoncontrolled and monitored liquid infusion.

During cataract surgery, the most common operation performed in theUnited States, the surgeon views only the anterior chamber of the eye asshown in FIG. 5, having no method of simultaneously monitoring theposterior segment.

Since the anterior chamber is quite small, containing only 0.25 cc ofliquid volume, small and momentary aspiration flow rates exceedinginfusion rates will result in anterior chamber collapse, as shown inFIG. 5. The consequence of anterior chamber collapse is damage to thenonreproducible monolayer of cells (endothelium) which lines the innersurface of the cornea, keeping it clear of fluid. This endothelialdamage can then result in clouding of the cornea, with the need forsubsequent cornea transplantation.

It is common for cataract surgeons to perform incomplete temporaryclosure of the surgical incision prior to irrigation/aspiration cataractcortex removal. A true "closed-eye" system is never achieved, andanterior chamber collapse in this condition is a sign of wound leakageof infusion liquids rather than of inadequate infusion pressure. Ifanterior chamber collapse is encountered, the wound should be checkedfor tightness.

The cataract surgeon's most common defense against perceived anteriorcollapse is increasing of infusion pressure by raising a gravity-feedinfusion bottle an estimated height above the eye as shown i n FIG. 4.Note that gas is not commonly infused into the anterior chamber in suchsurgery. In practice, bottle height is not measured, so that actualpressure delivered to the eye is unknown, and is presumed to besufficient when anterior chamber collapse no longer occurs.

Unfortunately, corneal endothelial damage may also occur as a result ofhigh infusate volume or jetstream mechanical damage from the use of highflow rates under high pressure. These effects, moreover, are not readilyapparent to the surgeon due to his inability to perceive the flow rateor pressure. Retinal artery occlusion may also occur, invisible to thesurgeon and resulting in blindness. Finally, iris prolapse through thewound may occur as a result of excessive infusion pressure.

Ideally, cataract irrigation/aspiration surgery should be performed withnormal ocular pressure (25 mm Hg). Failing this, infusion pressureshould be raised as little as possible to maintain anterior chamberpressure to avoid collapse during active irrigation/aspiration. Becauseunnecessarily high infusion pressure and flow rates can injure retinaland corneal tissues with little warning to the surgeon, increasinginfusion to the eye should be the last solution attempted to remedyanterior chamber collapse. As previously stated, the surgeon shouldfirst check adequate wound closure. Further, even with an adequatelyclosed eye, anterior chamber collapse may occur as a result ofundisciplined, continuous, high rate aspirations. High vacuum aspirationis necessary to achieve cataract removal, but successful removal ofblocks of cataract cortex material (with subsequent opening of theaspiration port) should be anticipated so as to intermittently reducethe aspiration vacuum, avoiding anterior chamber collapse. All toocommonly surgeons move about within the eye with an open aspirationport, with suction continuously engaged.

The above discussion demonstrates the importance of a new method ofrapid, accurate, surgeon-controlled ocular infusion (Gas Forced LiquidInfusion, GFLI).

SUMMARY OF THE INVENTION

The primary object of the invention is to provide the surgeon with amethod and apparatus to rapidly and precisely control and monitor hisinfusion pressure.

It is also an object of the present invention to enable the surgeon toquickly switch between liquid infusion and gas infusion.

Yet another object of the invention is to enable the usage of momentarymaximum safe infusion pressure for such purposes as controlling bleedingduring surgery.

These and other objects and advantages are accomplished in our inventionthrough a novel arrangement of conduits and valves which allow theconstant maintenance of the desired intraocular pressure and theflexibility of using either gas or liquid infusion. The inventionutilizes an infusion bottle as a reservoir for the infusion liquid. Acontinuous infusion gas pump, such as a Grieshaber or Trek Air Pump, isutilized to pressurize the liquid infusion bottle to the desiredinfusion pressure (Gas Forced Liquid Infusion, GFLI). The output of thepump is also used directly to provide pressurized gas via a conduit forgas infusion to the eye. A conduit from the infusion bottle providespressurized liquid for infusion. The gas conduit and liquid conduit arepreferentially formed as a dual-tube conduit and are connected to astopcock which allows the physician to select either gas infusion orliquid infusion.

In an alternate embodiment, adapted for anterior chamber surgery, thegas infusion line is eliminated since gas infusion is not commonly usedin this type surgery; the flexible conduit connections between theliquid infusate bottle and the eye, and between the gas pressure deviceand the liquid infusate bottle are maintained. In both embodiments, theoutput of the gas pump is connected directly to the pressurized gaspocket above the infusion liquid via a conduit extending within theliquid infusion bottle.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatus embodying features of our invention are depicted in theappended drawings which form a portion of this invention and wherein:

FIG. 1 is a perspective view showing the apparatus as used duringsurgery;

FIG. 2 is a broken lay-out view showing the invention not in use;

FIG. 3 is a broken lay-out view showing the cataract surgery embodiment;

FIG. 4 shows the prior art and ocular structures; and

FIG. 5 shows an instance of ocular collapse.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 4 illustrates the common control methodology and apparatus forliquid infusion of the eye as heretofore used in cataract and invitreous surgery. FIG. 5 is illustrative of common ocular collapse whenusing the method and apparatus shown in FIG. 4.

Referring to the figures for a better understanding of the invention, itmay be seen that the invention is for use with a patient who is lyingbeneath surgical drapes 11 on an operating table 12. A continuousinfusion air/gas pump 13 is located on an equipment stand 14 as isconventional practice. The output of the air/gas pump 13 is displayed asby LED's at a panel 16 so that the pressure generated thereby may bemonitored by the surgery team and precisely controlled.

The output of the air/gas pump 13 is used to pressurize a liquidinfusion bottle 23 to provide Gas Forced Liquid Infusion (GFLI) of theeye. Use of Gas Forced Liquid Infusion (with digital numeric readout ofinfusion pressure in view of the surgeon) allows the surgeon for thefirst time to accurately and continuously monitor this most importantparameter. In this method, the infusion bottle is hung at eye height, sothat gravity feed, the preferred technique of the prior art, contributesno pressure to perfusion/infusion. Rather, total control of perfusionpressure is instead achieved by instilling in the infusate bottle, gasunder pressure, provided by the gas pump. The infusion pressure canthereby be meticulously and rapidly selected by the surgeon.

An antibacterial filter connector 17 attaches a flexible conduit to thepump 13 in any conventional manner as is well known in the art. Theconduit 18 extends from the equipment stand 14 to near an IV support 19and terminates in a T-connector 21 or other suitable device fordirecting the airflow from the pump 13 along two paths. A fluidpressurization conduit 22 is connected between the T-connector 21 and acombined infusion bottle with drip chamber 23 supported by the IVsupport 19 and serves to pressurize the fluid therein in accordance withthe output pressure of the pump 13. This fluid pressurization conduitextends within the infusion bottle so as to connect the gas volume aboveliquid with the gas pump for venting purposes. A fluid delivery conduit24 is connected as the output of infusion bottle 23 and terminates asone input to infusate stopcock selection valve 26. An air deliveryconduit 27 is connected between the remaining branch of the T-connector21 and the valve 26. Note that valve 26 may be a three-way input valvewhich would allow selection of either liquid, air, or finally an air/gasmixture (e.g. sulfur hexafluoride SF.sub. 6 20%, perfluoropropane C₃ F₈15%) delivered by a second gas pump. The valve 26 has a single output toan infusion conduit 28 which is connected to and supplies an eyeinfusion cannula 29.

As shown in FIG. 1, the infusion bottle 23 is placed at the patient'seye level so as to contribute no gravity infusion pressure as had beencustomary in the prior art. Air/gas is pumped into the bottle 23 viaconduits 18 and 22 to provide the desired infusion pressure. Although anormal starting pressure may be selected, it should be clear that theinfusion pressure can be rapidly changed by adjusting the outputpressure of the air pump 13. The air pump selected should have a digitaldisplay 16 of the pressure which should be visible to all operating roompersonnel. It has been determined that the displayed, conduit, andintraocular static pressures agree to within two to four mm of Hg usingthe present apparatus.

Valve 26 allows the surgical team to quickly switch from liquid infusionto gas infusion. Conduits 24 and 27 may be formed from the two halves ofa twin plastic tube, for example Dicoc Twin Bore Silicone IV tubing,such that the valve 26 may be located immediately proximal to the shortcannula 29, thereby minimizing the time and volume required to clearinfusion liquid from the system cannula 29 when gas is desired.

From the foregoing, it may be seen that we have provided an effectiveapparatus and method (Gas Forced Liquid Infusion, GFLI) which greatlyimproves the surgeon's efficiency in vitrectomy operations in whichliquid to gas infusion changes are desired and also provides a readilycontrollable means for varying the infusion pressure during all liquidinfusion eye surgery including cataract removal. As is well known, it ispossible to stop or reduce bleeding by raising the intraocular pressureto maximum known safe levels, usually 35 to 45 mm of Hg. Using thepresent invention with a digital display 16 allows the surgical team toquickly determine the infusion pressure levels and rapidly change thelevel as required, to maximum safe level with great accuracy.

It is the aspect of the invention that allows the surgical team tocontinuously monitor and precisely control the infusion pressure whichis of critical importance to the cataract surgeon. The tubing systemshown in FIG. 3 uses an antibacterial filter connector 31 to attach aflexible tubing 32 to the air pump 13. The flexible tubing 32 isconnected directly to the infusion bottle 23 which is supplied withinfusion liquid as shown in FIG. 2. A single flexible conduit 33 isprovided to carry pressurized infusion liquid from the bottle to a valve34 which controls the flow of liquid to the infusion/aspiration device36 used in cataract surgery. With the digital readout 16 available, thesurgeon is able to constantly monitor the pressure being utilized in theeye and therefore is at all times aware of and alert to the potentialdeleterious consequences of overpressurization and jetstreaming. Thus,due to his ability to monitor and accurately select the intraocularpressure, the surgeon will naturally turn more attention to adequatewound closure and disciplined aspiration rather than using a potentiallydestructive infusion pressure level to prevent ocular collapse.

The use of the gas pump -3 to pressurize the infusion bottle 23 ineither of the embodiments above also leads to a significant furtherrefinement in the art. Voice recognition technology can be used toregulate the output pressure of the gas pump 3. Thus, an inputmicrophone 37 is connected to a voice recognition circuit, many of whichare commercially available, which in turn outputs a control signal tothe pump 13. Preferentially the pump will be provided with a speaker 38which will enunciate the pressure, subsequent to an instruction tochange pressure or upon a query by the surgeon; or upon a variance ofthe pressure outside a predetermined tolerance. The surgeon's voice mayspecifically recognized so that he might state the desired pressure inan audible voice, and the machine would respond immediately that it willseek the commanded pressure after a preset safety delay, in the absenceof further commands. Infusate selector valve 26 may also be voiceactuated. For the first time, perfusion pressure to the eye and infusatesource can be controlled directly by the surgeon rather thannecessitating the presence of other operating room personnel. Immediatepressure adjustment with voice response completes surgeon control ofinfusion pressure--the most vital parameter characterizing "closed-eye"surgery.

While we have shown our invention in two forms, it will be obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without departing from the spiritthereof.

We claim:
 1. An apparatus for controlling intraocular pressure duringclosed wound intraocular surgery, using a source of continuouspressurized gas at a controlled variable gas pressure, a liquid infusatereservoir having a limited volume for maintaining liquid infusate in thereservoir under pressure with a volume of gas, and an ocular surgicalinfusion instrument, comprising:(a) a first conduit for conveyingpressurized gas from the source of continuous pressurized gas to theliquid infusate reservoir; (b) a second conduit for conveying liquidinfusate from the reservoir to the ocular surgical infusion instrument;(c) a third conduit for conveying pressurized gas from the source ofcontinuous pressurized gas to the ocular surgical infusion instrument;and (d) an infusate selector valving means for selectively connectingeither said second or third conduit to the ocular surgical infusioninstrument such that when said second conduit is connected to thesurgical infusion instrument, pressurized gas from the source ofcontinuous pressurized gas is prevented from being conveyed to theinfusion instrument, and when said third conduit is connected to thesurgical infusion instrument, liquid infusate from the liquid infusatereservoir is prevented from being conveyed to the infusioninstrument;thereby permitting accurate and rapid control of infusionpressure during intraocular surgery and permitting rapid conversionbetween liquid and gas infusion during such surgery.
 2. An apparatus asdefined in claim 1 wherein said second conduit is connected to theliquid infusate reservoir for receiving liquid therefrom and is alsoconnected to said infusate selector valving means.
 3. An apparatus asdefined in claim 2 wherein said third conduit receives pressurized gasfrom the source of continuous pressurized gas and is connected to saidinfusate selector valving means.
 4. An apparatus as defined in claim 3wherein said infusate selector valving means comprises a valve having afirst inlet connected to said second conduit and a second inletconnected to said third conduit and an outlet connected to the ocularsurgical infusion instrument such that liquid or gas from said second orthird conduit may be selectively conveyed to the ocular surgicalinfusion instrument.
 5. An apparatus as defined in claim 4 wherein eachof said conduit members comprise a length of flexible silicone tubing.6. An apparatus as defined in claim 4, wherein said second and thirdconduit are formed from twin-bore silicone tubing with one bore servingas a conduit for the liquid infusate and with the other bore serving asa conduit for gas.
 7. An apparatus for controlling intraocular pressureduring closed wound intraocular surgery, using a source of continuouspressurized gas at a controlled variable gas pressure, a liquid infusatereservoir having a limited volume for maintaining liquid infusate in thereservoir under pressure with a volume of gas, and an ocular surgicalinfusion instrument, comprising:(a) a first conduit for conveyingpressurized gas from the source of continuous pressurized gas to theliquid infusate reservoir, with said conduit for conveying thepressurized gas extending into the volume of gas contained within thereservoir so that the volume of gas contained within the reservoir is indirect communication with the source of continuous pressurized gas; (b)a second conduit for conveying liquid infusate from the reservoir to theocular surgical infusion instrument; (c) a third conduit for conveyingpressurized gas from the source of continuous pressurized gas to theocular surgical infusion instrument; and (d) an infusate selectorvalving means for selectively connecting either said second or thirdconduit to the ocular surgical infusion instrument such that when saidsecond conduit is connected to the surgical infusion instrument,pressurized gas from the source of continuous pressurized gas isprevented from being conveyed to the infusion instrument, and when saidthird conduit is connected to the surgical infusion instrument, liquidinfusate from the liquid infusate reservoir is prevented from beingconveyed to the infusion instrument; thereby permitting accurate andrapid control of infusion pressure during intraocular surgery andpermitting rapid conversion between liquid and gas infusion during suchsurgery.
 8. An apparatus for controlling intraocular pressure duringclosed wound intraocular surgery, using a source of continuouspressurized gas at a controlled variable gas pressure, a liquid infusatereservoir having a limited volume for maintaining liquid infusate in thereservoir under pressure with a volume of gas, and an ocular surgicalinfusion instrument, comprising:(a) a first conduit for conveyingpressurized gas from the source of continuous pressurized gas to theliquid infusate reservoir; (b) a second conduit for conveying liquidinfusate from the reservoir to the ocular surgical infusion instrument;(c) a third conduit for conveying pressurized gas from the source ofcontinuous pressurized gas to the ocular surgical infusion instrument;(d) an infusate selector valving means for selectively connecting eithersaid second or third conduit to the ocular surgical infusion instrumentsuch that when said second conduit is connected to the surgical infusioninstrument, pressurized gas from the source of continuous pressurizedgas is prevented from being conveyed to the infusion instrument, andwhen said third conduit is connected to the surgical infusioninstrument, liquid infusate from the liquid infusate reservoir isprevented from being conveyed to the infusion instrument; and (e) a gaspressure control means for variably controlling the pressure of the gasfrom the source of continuous pressurized gas by audible commandsignals;thereby permitting accurate and rapid control directly by thesurgeon of infusion pressure during intraocular surgery and permittingrapid conversion between liquid and gas infusion during such surgery. 9.An apparatus as defined in claim 8 further comprising an indicationmeans in connection with said gas pressure control means for providing ahuman audible indication of the pressure of the gas from the source ofcontinuous pressurized gas.
 10. An apparatus as defined in claim 8wherein said gas pressure control means for variably controlling thepressure of the gas from the source of continuous pressurized gasprovides an audible signal acknowledging a detected audible commandsignal.
 11. An apparatus as defined in claim 8 further comprising avalve position control means connected to said infusate selector valvingmeans for selectively controlling the connection of either said secondor third conduit to the ocular surgical infusion instrument by audiblecommand signals.
 12. An apparatus as defined in claim 8 wherein saidfirst conduit for conveying the pressurized gas to the liquid infusatereservoir extends into the volume of gas contained within the reservoirso that the volume of gas contained within the reservoir is in directcommunication with the source of continuous pressurized gas.
 13. Anapparatus for controlling intraocular pressure during closed woundintraocular surgery, using a source of continuous pressurized gas at acontrolled variable gas pressure, a liquid infusate reservoir having alimited volume for maintaining liquid infusate in the reservoir underpressure with a volume of gas, and an ocular surgical infusioninstrument, comprising:(a) a first conduit for conveying pressurized gasfrom the source of continuous pressurized gas to the liquid infusatereservoir such that the pressure within the liquid infusate reservoir issubstantially the same as the pressure produced by the source ofcontinuous pressurized gas; (b) a second conduit for conveying liquidinfusate from the reservoir to an ocular surgical infusion instrument;and (c) a valving means in communication with said second conduit forcontrolling the flow of liquid infusate from the liquid infusatereservoir to the ocular surgical infusion instrument; thereby permittingaccurate and rapid control of infusion pressure during intraocularsurgery and avoiding the deleterious consequences of underpressurizationor overpressurization and jetstreaming during such surgery.
 14. Anapparatus as defined in claim 13 wherein each of said conduit memberscomprise a length of flexible silicone tubing.
 15. An apparatus forcontrolling intraocular pressure during closed wound intraocularsurgery, using a source of continuous pressurized gas at a controlledvariable gas pressure, a liquid infusate reservoir under pressure with avolume maintaining liquid infusate in the reservoir under pressure witha volume of gas, and an ocular surgical infusion instrument,comprising:(a) a first conduit for conveying pressurized gas from thesource of continuous pressurized gas to the liquid infusate reservoirsuch that the pressure within the liquid infusate reservoir issubstantially the same as the pressure produced by the source ofcontinuous pressurized gas, with said conduit for conveying thepressurized gas extending into the volume of gas contained within thereservoir so that the volume of gas contained within the reservoir is indirect communication with the source of continuous pressurized gas; (b)a second conduit for conveying liquid infusate from the reservoir to theocular surgical infusion instrument; and (c) a valving means incommunication with said second conduit for controlling the flow ofliquid infusate from the liquid infusate reservoir to the ocularsurgical infusion instrument;thereby permitting accurate and rapidcontrol of infusion pressure during intraocular surgery and avoiding thedeleterious consequences of underpressurization or overpressurizationand jetstreaming during such surgery.
 16. An apparatus for controllingintraocular pressure during closed wound intraocular surgery, using asource of continuous pressurized gas at a controlled variable gaspressure, a liquid infusate reservoir having a limited volume formaintaining liquid infusate in the reservoir under pressure with avolume of gas, and an ocular surgical infusion instrument,comprising:(a) a first conduit for conveying pressurized gas from thesource of continuous pressurized gas to the liquid infusate reservoirsuch that the pressure within the liquid infusate reservoir issubstantially the same as the pressure produced by the source ofcontinuous pressurized gas; (b) a second conduit for conveying liquidinfusate from the reservoir to the ocular surgical infusion instrument;(c) a valving means in communication with said second conduit forcontrolling the flow of liquid infusate from the liquid infusatereservoir to the ocular surgical infusion instrument; and (d) a gaspressure control means for variably controlling the pressure of the gasfrom the source of continuous pressurized gas by audible commandsignals;thereby permitting accurate and rapid control directly by thesurgeon of infusion pressure during intraocular surgery and avoiding thedeleterious consequences of underpressurization or overpressurizationand jetstreaming during such surgery.
 17. An apparatus as defined inclaim 16 further comprising an indication means, in connection with saidgas pressure control means, for providing a human audible indication ofthe pressure of the gas from the source of continuous pressurized gas.18. An apparatus as defined in claim 16 wherein said gas pressurecontrol means for variable controlling the pressure of the gas from thesource of continuous pressurized gas provides an audible signalacknowledging a detected audible command signal.
 19. An apparatus asdefined in claim 16 wherein said first conduit for conveying thepressurized gas to the liquid infusate reservoir extends into the volumeof gas contained within the reservoir so that the volume of gascontained within the reservoir is in direct communication with thesource of continuous pressurized gas.
 20. A method of ocular perfusionusing Gas Forced Liquid Infusion (GFLI), comprising:(a) continuouslysupplying pressurized gas at a selected variable pressure from a sourceof continuous pressurized gas having a control means to vary gaspressure; (b) pressurizing the contents of a liquid infusate reservoirwith the pressurized gas so that the pressurized gas output from thesource of pressurized gas is in direct communication with a pressurizedgas pocket within the liquid infusate reservoir; (c) supplying theliquid contents of the liquid infusate reservoir to an ocular surgicalinfusion instrument for infusion into a selected anterior or posteriorocular chamber as in infusate; (d) selectively varying the pressure ofthe infusate within the selected anterior or posterior ocular chamber bycontrolling the pressure of the gas from the source of continuouspressurized gas; and (e) supplying pressurized gas from the pressurizedgas source to the ocular surgical infusion instrument and selectivelyinfusing the selecting anterior or posterior ocular chamber with gas orliquid infusate;thereby permitting accurate and rapid control ofinfusion pressure during intraocular surgery and permitting rapidconversion between liquid and gas infusion during such surgery.
 21. Amethod of ocular perfusion using Gas Forced LIquid Infusion (GFLI),comprising:(a) continuously supplying pressurized gas at a selectedvariable pressure from a source of continuous pressurized gas having acontrol means to vary gas pressure; (b) pressurizing the contents of aliquid infusate reservoir with the pressurized gas; (c) supplying theliquid contents of the liquid infusate reservoir to an ocular surgicalinfusion instrument for infusion into a selected anterior or posteriorocular chamber as an infusate; (d) selectively varying the pressure ofthe infusate within the selected anterior or posterior ocular chamber bycontrolling the pressure of the gas from the source of continuouspressurized gas; (e) supplying pressurized gas from the pressurized gassource to the ocular surgical infusion instrument and selectivelyinfusing the selected anterior or posterior ocular chamber with gas orliquid infusate; and (f) controlling the pressure of the gas from thesource of continuous pressurized gas by audible command signalsdetectable by a gas pressure control means which varies gas pressure inaccordance with the detected audible command signal;thereby permittingaccurate and rapid control directly by the surgeon of infusion pressureduring intraocular surgery and permitting rapid conversion betweenliquid and gas infusion during such surgery.
 22. A method as defined inclaim 21 wherein the pressure of the gas supplied from the source ofcontinuous pressurized gas is indicated by a human audible signal.
 23. Amethod as defined in claim 21 wherein said control of the pressure ofthe gas from the source of continuous pressurized gas by audible commandsignals includes a human audible signal acknowledging the detectedaudible command signal.
 24. A method as defined in claim 21 wherein saidselective infusion of the ocular chamber with gas or liquid infusate isaccomplished by audible commands detectable by a valve position controlmeans which selectively connects pressurized gas from the source ofcontinuous pressurized gas or liquid infusate from the liquid infusatereservoir to an ocular surgical infusion instrument in accordance withthe detected audible command signal.
 25. A method as defined in claim 21wherein said pressurization of the contents of the liquid infusatereservoir is accomplished with the pressurized gas output from thesource of continuous pressurized gas in direct communication with thepressurized gas pocket within the liquid infusate reservoir.
 26. Amethod of ocular perfusion using Gas Forced Liquid Infusion (GFLI),comprising:(a) a continuously supplying pressurized gas at a selectedvariable pressure from a source of continuous pressurized gas having acontrol means to vary gas pressure; (b) pressurizing the contents of aliquid infusate reservoir directly with the pressurized gas such thatthe pressure within the liquid infusate reservoir is substantially thesame as the pressure produced by the source of continuous pressurizedgas; (c) supplying the liquid contents of the liquid infusate reservoirto an ocular surgical infusion instrument for infusion into a selectedanterior or posterior ocular chamber as an infusate; and (d) selectivelyvarying the pressure of the infusate within the selected anterior orposterior ocular chamber by controlling the pressure of the gas from thesource of continuous pressurized gas;thereby permitting accurate andrapid control of infusion pressure during intraocular surgery andavoiding the deleterious consequences of underpressurization oroverpressurization and jetstreaming during such surgery.
 27. A method ofocular perfusion using Gas Forced Liquid Infusion (GFLI), comprising:(a)continuously supplying pressurized gas at a selected variable pressurefrom a source of continuous pressurized gas having a control means tovary gas pressure; (b) pressurizing the contents of a liquid infusatereservoir directly with the pressurized gas such that the pressurewithin the liquid infusate reservoir is substantially the same as thepressure produced by the source of continuous pressurized gas and sothat the pressurized gas output from the source of pressurized gas is indirect in communication with a pressurized gas pocket within the liquidinfusate reservoir; (c) supplying the liquid contents of the liquidinfusate reservoir to an ocular surgical infusion instrument forinfusion into a selected anterior or posterior ocular chamber as aninfusate; and (d) selectively varying the pressure of the infusatewithin the selected anterior or posterior ocular chamber by controllingthe pressure of the gas from the source of continuous pressurizedgas;thereby permitting accurate and rapid control of infusion pressureduring intraocular surgery and avoiding the deleterious consequences ofunderpressurization or overpressurization and jetstreaming during suchsurgery.